Investigation of Poly Film Application in Advanced MOSFET Technology

Abstract

Un-doped poly process becomes more critical with CMOS scaling down as gate electrode in advanced Poly/SiON process and dummy poly in HK/MG technology. The poly grain size and roughness impact the device mis-match between different transistors like NMOS off current fluctuation and it plays as dummy poly role in HK/MG technology. It is necessary to investigate the poly grain size after deposition and thermal process as it will change the poly grain structure. In this paper, top view Scanning Electrical Microscope (SEM), X-ray Diffraction (XRD),Atomic Force Microscopy (AFM) and Transmission Electron Microscope (TEM) are used to characterize the poly grain size, crystalline fraction, surface roughness and poly structure. It is find that the poly grain becomes larger after thermal, especially spike anneal. A smaller grain size of undoped poly with lower roughness was achieved by process tuning of temperature, pressure, gas flow etc which was implemented in device wafer and get improved performance.